A fuel cell system is a power generation system that directly converts chemical energy of fuel into electricity. A fuel cell system includes: a fuel cell stack that generates electricity; a fuel supply unit that supplies the fuel cell stack with fuel (i.e. hydrogen); an air supply unit that supplies the fuel cell stack with air (i.e. oxygen) serving as oxidant which causes an electrochemical reaction; and a heat-and-water management unit that discharges heat out of the fuel cell stack and controls the operation temperature of the fuel cell stack. The fuel cell stack produces electricity through an electrochemical reaction between hydrogen (fuel) and oxygen (air) and also generates byproducts (heat and water) that need to be discharged out of the fuel cell stack.
A fuel cell stack that is suitably used for a fuel cell vehicle includes many single cells arranged in a row. Each single cell includes a membrane-electrode assembly (MEA) disposed in the center. The MEA includes an electrolyte membrane that allows protons to pass therethrough. Catalyst layers serving as a cathode and an anode at which hydrogen and oxygen react with each other are provided on respective surfaces of the electrolyte membrane. Gas diffusion layers (GDL) are disposed on the surfaces of the catalyst layers. Separators with respective flow fields (channels) through which fuel and air are supplied to the anode and the cathode are disposed on the surfaces of the GDLs. End plates are disposed at respective ends of a single cell to firmly combine the all elements.
In the fuel cell stack, hydrogen and oxygen are ionized through chemical reactions by catalyst layers. Then, an oxidation reaction occurs to generate protons (hydrogen ions) and electrons at a fuel electrode to which hydrogen is supplied. A reduction reaction involving hydrogen ions and oxygen ions occurs to produce water at an air electrode to which air is supplied. A typical electrode catalyst that is used for a fuel cell is composed of a catalyst support made from a carbon material and a cocatalyst such as Ru, Co, Cu, or the like. Hydrogen is supplied to an anode (also referred to as “oxidation electrode”) and oxygen (air) is supplied to a cathode (also referred to as “reduction electrode”). Hydrogen supplied to the anode is split into protons H+ and electrons e− by catalysts on electrode layers disposed on respective surfaces of the electrolyte membrane. Of the protons and electrons, only protons can selectively pass through an electrolyte membrane called a proton exchange membrane and can reach a cathode, and electrons move through the GDLs (conductive layers) and separators to reach the cathode.
Hydrogen ions and electrons that reach the cathode through the electrolyte membrane and separators combine with oxygen contained in air that is supplied to the cathode by an air supply unit, thereby producing water. At this point, movement of hydrogen ions induces an electric current that flows along an external wire. At this point, aside from water, heat is also concomitantly produced as a byproduct.
Typically, an enclosure houses and seals a fuel cell stack that provides a high voltage to physically protect the fuel cell stack. In this case, water may be produced in the enclosure due to condensation that is attributable to a difference in temperature between an inside and an outside of the enclosure. Furthermore, water that is produced by a fuel cell stack disposed in the enclosure may gather in the enclosure. Therefore, an effective means for discharging water that is produced by a fuel cell stack as well as water that is generated due to condensation is needed.
Conventionally, a water outlet for discharging water is formed in a lower housing of an enclosure as the means for discharging water out of the enclosure. The conventional water-discharging means has a problem that it may allow contaminants to enter the enclosure, which often leads to malfunctioning of a fuel cell stack disposed in the enclosure. Furthermore, as for conventional enclosures, water removal efficiency is dependent on the position, size, and number of water outlets. That is, as the number of water outlets increases, the water removal effect is improved but sealing performance is deteriorated.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.